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Batteries and being off grid


rowland al

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4 minutes ago, Naughty Cal said:

Despite all of the mix up with units, I'm actually interested how long this single 75AH starter battery is going to last being used as a leisure battery in daily use.

My initial thoughts would be not very long.

I’d go along with your initial thoughts ;)

I had to laugh when OP wrote “I disagree Tony” after he’d been corrected over his incorrect use of units. :D

 

Edited by WotEver
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4 minutes ago, Naughty Cal said:

Despite all of the mix up with units, I'm actually interested how long this single 75AH starter battery is going to last being used as a leisure battery in daily use.

 

So am I!

BTW, actually an amp (ampere) is a rate too. A coulomb is a quantity. 

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2 minutes ago, rowland al said:

BTW, actually an amp (ampere) is a rate too. A coulomb is a quantity. 

Yes, an amp is indeed a rate, which is why you can’t use it as a quantity. 

“I used 35 miles per gallon on my last trip”

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6 minutes ago, rowland al said:

So am I!

BTW, actually an amp (ampere) is a rate too. A coulomb is a quantity. 

John Noakes went up Nelsons Coulomb once. From up there I bet the people looked like ants. I reckon if he had counted them, he would have seen 1000 ants/hour. I suspect he was rather busy bricking it instead.

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1 hour ago, Alan de Enfield said:

Jeremiah 5:21

'Hear now this, O foolish people, and without understanding; which have eyes, and see not; which have ears, and hear not'.

John Heywood - 1546

"There are none so blind as those who will not see. The most deluded people are those who choose to ignore what they already know

Here's another proverb for you.

"Nobody likes a smart arse". :)

 

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3 hours ago, rowland al said:

I don't really agree Tony. To say I use say 20 amps over 6 hours (evenings use) is a rate!

I could say my consumption is 3.33ah if that's better? However it isn't. It might be 5ah in one hour and 1ah in another.

BTW, thanks again for your help in getting me here  :) 

Maybe this will help the understanding of the units of capacity / consumption.

A current of one amp for one hour is 1Ah (Amp Hour)

A current of 2 amps for 1/2 hour is one 1Ah

A current of 20 amps for 3 mins is 1Ah

If you have an average current of 3.33A for 6 hours that would be 19.98Ah  (3.33A multiplied by 6 - the time in hours)

Likewise if you use 20Ah over an evening you have taken 20Ah out of your battery.  Now some people will (wrongly) shorten Ah to just amps, and whilst people may guess what you mean, they may be wrong, so one should always use the correct name for units.  So for example, when my headlight is on it uses 35W which is a current of about 2.8A (assuming a supply voltage of 12.5v)  so I have a current of 2.8A.  If I use it for 2 hours in a tunnel I have used 2.8 (amps) multiplied by 2 (hours) which gives me 5.6Ah.  So you can see that if you say you used 5.6A people will be confused as they know the lamp draws about 2.8A, but when say you used 5.6Ah and everything is clear.

Added - You can use other units of time if you want, such as Amp Minutes or Amp Days, but nobody normally does, so best you don't.  When doing a power usage estimate for short duration loads like water pumps, microwaves etc I will estimate in amp minutes as I find it easier to do this in my head, but when I have added them all up I convert to amp hours.

 

 

Edited by Chewbacka
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54 minutes ago, Chewbacka said:

Maybe this will help the understanding of the units of capacity / consumption.

A current of one amp for one hour is 1Ah (Amp Hour)

A current of 2 amps for 1/2 hour is one 1Ah

A current of 20 amps for 3 mins is 1Ah

If you have an average current of 3.33A for 6 hours that would be 19.98Ah  (3.33A multiplied by 6 - the time in hours)

Likewise if you use 20Ah over an evening you have taken 20Ah out of your battery.  Now some people will (wrongly) shorten Ah to just amps, and whilst people may guess what you mean, they may be wrong, so one should always use the correct name for units.  So for example, when my headlight is on it uses 35W which is a current of about 2.8A (assuming a supply voltage of 12.5v)  so I have a current of 2.8A.  If I use it for 2 hours in a tunnel I have used 2.8 (amps) multiplied by 2 (hours) which gives me 5.6Ah.  So you can see that if you say you used 5.6A people will be confused as they know the lamp draws about 2.8A, but when say you used 5.6Ah and everything is clear.

Added - You can use other units of time if you want, such as Amp Minutes or Amp Days, but nobody normally does, so best you don't.  When doing a power usage estimate for short duration loads like water pumps, microwaves etc I will estimate in amp minutes as I find it easier to do this in my head, but when I have added them all up I convert to amp hours.

 

 

So I guess that quoting that we use roughly 20,000 coulombs of electrical charge most evenings is out of the question then? ;)

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Ignoring the argument regarding the correct method of expressing energy usage. Some real world information.

This year we changed the way we use our boat, for twelve years it has been used for holidays and weekends, for that purpose six 110 Amp Hr Numax leisure batteries have been satisfactory, the first set lasting nearly eight years, we replaced them with the same type.

This year we used the boat as liveaboards cruising from  Newbury to Leeds covering all the waterways we could on the way. It became very obvious early on in the journey that the now four year old batteries were not performing as we needed. We have a Smartgauge and a Smartbank fitted, so we know we were charging correctly but we were dropping to around 60% after a nights use. We have all LED lights but the fridge and TV both run from a PSW inverter. The fridge was the problem even though it was new A+ unit it could easily cause the inverter to trip not long after we had moored up because the compressor starting current was greater than the batteries could supply to the inverter.

I replaced the six Numax batteries with five 170 Amp Hr traction batteries, these are flooded tubular plate beasts, they weigh twice as much as the Numax at 40 kilos each. The difference is amazing a nights use sees a drop of less than 5 % on the Smartgauge and the fridge has been tamed.

We have had this discussion many times but so called leisure batteries are for the most part simply larger starter batteries and therefore not ideal as domestic batteries, easy to tell, if there is a CCA figure quoted in the description it is a starter battery. Traction batteries are more expensive but they work and provided they are looked after will last longer.

I have no idea how the OP uses his boat but my experience suggests that for liveaboard use a simple starter battery will have a short life as they are simply not designed to be used as domestic batteries.

 

Ken

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36 minutes ago, Chewbacka said:

It would be easier to say (from memory, so may have converted wrongly) about 5.5Ah, which is pretty frugal.

Online calculators say 5.5555555Ah so I’d say you’re pretty close ;)

At least it’s a measure of consumption over time as opposed to an instantaneous reading. 

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4 hours ago, WotEver said:

 

I had to laugh when OP wrote “I disagree Tony” after he’d been corrected over his incorrect use of units. :D

 

...    yes, I seem to remember I had a bit of a fizz on the forum when I started out [re steel]. I have survived...

I don't know much about electricity, but I know enough about wheels not to re-invent them :)

Edited by LadyG
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A BIT IMPORTANT.    I;ve checked with the patents office, and believe it or not the patent for the principal of ''The Crank'' has long expired. So I'm about to re-invent it. Meanwhile prepare to cease using engines in all modes of conveyances and in any othe implement whatsoever. This NOTISS applies to any mechanism that involves the principal of ''The Crank'' in the whole wide world and in space, ''NASA take note''   My intention is to bring the world to a standstill until  I've completed re-inventing and re-patenting  ''The Crank''. I shall take my time over the process which will allow the people of the world to swoon in peace, tranquility and jollyness from noisy stinky engines, mechanisms and the like. Completion of the process should be at about 2.04pm, 1st April, 2073. Until then start saving up to pay me my ''Royalties'' for allowing further use of the ''Principal of the CRANK''.  Ruyalty Payments to myself  ''Bizzard'' MUST be made payable to   (Messer Bizzard & Co Unlimited)   by Cash, postal order, cheque, bank transfer, debit or credit cards.  Stricktly No ''Easy terms'' .so don't bother asking.       By order of Messer Bizzard & Co Unlimited.   :mellow:  

Edited by bizzard
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